It seems that Sibelius wrote much of his piano music for domestic compsumtion and to earn some cash, but these works are worth exploring if you enjoy his far better-known orchestral music. Havard Gimse is an excellent pianist and has recorded all of Sibelius' piano music for Naxos on 5 CDs. The recorded sound, from 1997, is very good indeed and far better than earlier, problematic, Naxos piano CDs. The engineer and producer, Gary Cole, did wonders in St Martin's Church, East Woodhay, Hampshire on those April days. Gimse plays a Steinway and is caught in an ideal recording.
This CD, the first volume in the series, contains early works: these are the "Six Impromptus" Op.5, the Sonata in F major, Op.12, and "Ten Pieces", Op. 24. They date from 1893-1903. I find the first two works relatively minor pieces, but the "Ten Pieces" are rather more interesting (very high-grade Salon music?) as you can hear the strong suggestion of orchestral writing in them, for which, of course, Sibelius is revered.
This is a valuable recital of a little-known, but important, part of Sibelius' lifetime output. Recommended.